Identification of Salmonella using colony-print and detection with antibody-coated gold nanoparticles

In this study, we developed an easy screening test that identifies Salmonella in 2 h after colony-print which is a procedure based on the transfer of surface cells of the colonies to a nitrocellulose membrane. Gold nanoparticles coated with the anti-Salmonella antibody were used to highlight the Salmonella spp. on the membrane to facilitate the selectivity. On Hektoen agar, 134 stool samples containing black or crystalloid colonies were identified using the proposed method. Without any equipment, such as microscope, the red dots corresponding Salmonella were observed. After colony-print test, 22 of the isolates were correctly identified as Salmonella to achieve 100% sensitivity. 111 samples were correctly identified as non-Salmonella spp., but one was incorrectly identified as Salmonella. The specificity is 99.1%. This method is simple, straightforward, inexpensive, and fast. It can be easily applied to the routine workload of clinical laboratories, and can be very useful when large amounts of fecal samples should be evaluated for rapid screening and diagnosis.